A 730mpa grade ultra-high strength steel plate for high-rise buildings and a manufacturing method thereof

Abstract

The application discloses a 730MPa-grade ultra-high-strength high-rise building steel plate and a manufacturing method thereof, and belongs to the field of alloy steel manufacturing.The chemical components of the steel plate are as follows: C, Si, Mn, P, S, Cr, Ni, Cu, Nb, V, Ti, Al, and the balance of Fe and inevitable impurity elements.A low-C and micro-alloying method is adopted in the application, and a small amount of Cr, Ni and Cu elements are added; Nb and V micro-alloying elements are used to precipitate and separate out in a two-stage rolling process, so as to pin austenite grains, inhibit the growth of the austenite grains and refine the grain size; the rolling process is strictly controlled in the two-stage rolling process, and a subsequent rapid water cooling mode is controlled; through the control of a precise red temperature, a certain proportion of bainite and ferrite structures are obtained; the application has excellent comprehensive performance of low yield ratio, high strength, high elongation and high low-temperature toughness, and has important significance for the development of various building steel structures.

Description

Technical Field

[0001] This invention belongs to the field of alloy steel manufacturing and relates to a steel plate for high-rise buildings and its manufacturing method. Specifically, it relates to an ultra-high strength steel plate for high-rise buildings with a tensile strength of 730MPa and its manufacturing method. Background Technology

[0002] Steel structures are highly favored by the market due to their high strength, light weight, good seismic performance, ease of construction of large spans and large spaces, short construction cycle, more reliable quality, environmental friendliness, and reusability. With the development of high-rise, large-scale, and green building structures, ultra-high-strength steel with tensile strength of 730MPa or even higher has broad application prospects.

[0003] Currently, there are few applications of ultra-high strength medium-thick steel plates with a tensile strength of 730MPa in the construction industry, and there are also few related patents. Moreover, the production process mainly uses quenching and tempering. For example, the patent "A high-strength, high-toughness, easy-to-weld structural steel plate with a yield strength of 620MPa and its preparation method" published in CN 112813344 B uses a quenching + high-temperature tempering process to produce easy-to-weld structural steel plates with a yield strength of 620MPa. Its disadvantages are that the process is relatively complex and the yield strength ratio of the steel plates obtained is high, not less than 0.88.

[0004] The publication CN 115216681 A, entitled "A Production Method of Q620GJ with Low Yield-to-Toughness Ratio and High Toughness", describes a process for producing Q620GJ steel plates using online quenching and high-temperature tempering. Its disadvantages are that the process is relatively complex and the alloy element content is relatively high, so it is mainly used for the production of plates with a thickness of 80mm or more. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for preparing 730MPa grade ultra-high strength steel plates for high-rise buildings.

[0006] Technical Solution: This invention discloses a 730MPa grade ultra-high strength steel plate for high-rise buildings and its manufacturing method. The steel plate has the following mass percentages: C: 0.11%–0.13%, Si: 0.17%–0.30%, Mn: 1.61%–1.85%, P: ≤0.015%, S: ≤0.005%, Cr: 0.55%–0.85%, Ni: 0.30–0.50%, Cu: 0.15–0.30%, Nb: 0.040%–0.070%, V: 0.03%–0.06%, Ti: 0.010–0.020%, Al: 0.020–0.050%. The balance is Fe and unavoidable impurity elements.

[0007] Furthermore, the 730MPa grade ultra-high strength high-rise building steel plate has the following weight percentage composition: C: 0.11%, Si: 0.17%, Mn: 1.61%, P: 0.011%, S: 0.005%, Cr: 0.55%, Ni: 0.31%, Cu: 0.15%, Nb: 0.040%, V: 0.031%, Ti: 0.015%, Al: 0.021%. The balance is Fe and unavoidable impurity elements.

[0008] Furthermore, the 730MPa grade ultra-high strength high-rise building steel plate has the following weight percentage composition: C: 0.12%, Si: 0.24%, Mn: 1.76%, P: 0.013%, S: 0.003%, Cr: 0.74%, Ni: 0.39%, Cu: 0.22%, Nb: 0.058%, V: 0.043%, Ti: 0.010%, Al: 0.040%. The balance is Fe and unavoidable impurity elements.

[0009] Furthermore, the 730MPa grade ultra-high strength high-rise building steel plate has the following weight percentage composition: C: 0.13%, Si: 0.30%, Mn: 1.85%, P: 0.010%, S: 0.004%, Cr: 0.85%, Ni: 0.50%, Cu: 0.29%, Nb: 0.070%, V: 0.06%, Ti: 0.020%, Al: 0.048%. The balance is Fe and unavoidable impurity elements.

[0010] Furthermore, a method for manufacturing 730MPa grade ultra-high strength steel plates for high-rise buildings involves sequentially processing steel billets with the same composition as the 730MPa grade steel through a converter smelting process, an out-of-furnace refining process, and a continuous casting process to produce a 730MPa grade steel continuous casting billet with the target composition. The continuous casting billet then undergoes a slab heating furnace heating process, controlled rolling, controlled cooling, steel plate straightening, inspection, and warehousing. The specific steps are as follows:

[0011] (1) Heating regime of slab heating furnace: heating temperature is 1180~1220℃, total furnace time is 10~14min / cm, and uniform original austenitic structure is obtained inside the steel;

[0012] (2) Rolling process: Controlled rolling and cooling process is adopted, which is a two-stage controlled rolling process, namely rolling in the austenite recrystallization zone and the austenite non-recrystallization zone, with a total compression ratio of not less than 3 times: the rough rolling start temperature is ≥1080℃, and a large reduction method is adopted in this stage; the finish rolling start temperature is 900~930℃, and the thickness of the billet to be heated is not less than 3.0 times the thickness of the finished product. In this stage, by ensuring sufficient deformation, the austenite grains are stretched and deformed along the rolling direction. At the same time, by adding microalloying elements such as Nb and V, strain-induced precipitation of carbonitride particles is precipitated during this deformation process, which pins the austenite grains and prevents them from growing, thereby refining the microstructure after phase transformation and playing a certain precipitation strengthening role; the final rolling temperature is 860~890℃.

[0013] (3) Cooling process: After rolling, the water is quickly immersed and cooled by laminar flow. The water temperature is 820-850℃, and the final cooling temperature is 440℃-500℃. Then, it is air-cooled to room temperature.

[0014] Furthermore, the 730MPa grade ultra-high strength high-rise building steel plate described in this invention has a final microstructure of bainitic + ferrite, wherein the bainite content is 85%–90% and the ferrite content is 10%–15%. The steel plate possesses excellent comprehensive properties, including a low yield strength ratio, high strength, high elongation, and high and low temperature toughness.

[0015] Beneficial Effects: Compared with the prior art, the features of this invention are: 1. The 730MPa grade ultra-high strength high-rise building steel plate provided by this invention adopts a low-C, low-Fe, micro-alloying design, and adds a small amount of Cr, Ni, and Cu elements. Micro-alloying elements such as Nb and V precipitate during the two-stage rolling process, which pins austenite grains, inhibits austenite grain growth, and thus refines the grain size, while also providing a certain precipitation strengthening effect to ensure the high strength requirements of the steel plate; the addition of the high solid solution strengthening element Cr significantly improves the solid solution strengthening effect of the steel plate, and the appropriate addition of Ni element ensures the strength of the steel plate while significantly improving its low-temperature toughness. The addition of Cu element provides solid solution and precipitation strengthening, ultimately resulting in a high-performance steel plate; 2. The 730MPa grade ultra-high strength high-rise building steel plate provided by this invention adopts a controlled rolling and controlled cooling production process. The rolling process strictly controls the temperature and compression ratio of the two-stage rolling process, supplemented by a subsequent rapid water immersion controlled cooling method. By precisely controlling the red-hot temperature, a certain proportion of bainite and ferrite structure is obtained, while obtaining stable and excellent mechanical properties. The production process is short and the preparation method is simple; 3. The 730MPa grade ultra-high strength high-rise building steel plate has excellent comprehensive properties such as low yield strength ratio, high strength, high elongation, and high and low temperature toughness. Attached Figure Description

[0016] Figure 1This is the OM image of the microstructure of the 730MPa grade ultra-high strength high-rise building steel plate in the embodiment of the present invention. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Example 1:

[0019] The present invention discloses a 730MPa grade ultra-high strength steel plate for high-rise buildings, the chemical composition of which is as follows (mass percentage of each element): C: 0.11%, Si: 0.17%, Mn: 1.61%, P: 0.011%, S: 0.005%, Cr: 0.55%, Ni: 0.31%, Cu: 0.15%, Nb: 0.040%, V: 0.031%, Ti: 0.015%, Al: 0.021%. The balance is Fe and unavoidable impurity elements.

[0020] Furthermore, a method for preparing 730MPa grade ultra-high strength steel plates for high-rise buildings includes the following steps:

[0021] (1) The raw materials are smelted in a converter, refined outside the furnace and cast into a continuous casting billet to obtain a billet with a thickness of 220mm.

[0022] (2) The slab is placed in a heating furnace and heated at 1180℃ for a total time of 308 minutes.

[0023] (3) Two-stage rolling process is adopted: the rough rolling start temperature is 1081℃, the thickness of the billet is 60mm, the finish rolling start temperature is 900℃, the final rolling temperature is 860℃, and the steel plate with a thickness of 20mm is rolled.

[0024] (4) After rolling, the rolls are cooled by laminar flow cooling. The water temperature is 820℃, the final cooling temperature is 500℃, and then the rolls are cooled to room temperature by air.

[0025] Another preparation method includes the following steps:

[0026] (1) The raw materials are smelted in a converter, refined outside the furnace and cast into a continuous casting billet to obtain a billet with a thickness of 220mm.

[0027] (2) The slab is placed in a heating furnace and heated at 1180℃ for a total time of 308 minutes.

[0028] (3) Two-stage rolling process is adopted: the rough rolling start temperature is 1090℃, the thickness of the billet to be warmed is 120mm, the finish rolling start temperature is 905℃, the final rolling temperature is 880℃, and the steel plate with a thickness of 40mm is rolled.

[0029] (4) After rolling, the rolls are cooled by laminar flow cooling. The water temperature is 841℃, the final cooling temperature is 445℃, and then the rolls are cooled to room temperature by air.

[0030] Example 2:

[0031] The present invention discloses a 730MPa grade ultra-high strength steel plate for high-rise buildings, the chemical composition of which is as follows (mass percentage of each element): C: 0.12%, Si: 0.24%, Mn: 1.76%, P: 0.013%, S: 0.003%, Cr: 0.74%, Ni: 0.39%, Cu: 0.22%, Nb: 0.058%, V: 0.043%, Ti: 0.010%, Al: 0.040%. The balance is Fe and unavoidable impurity elements.

[0032] Furthermore, a method for preparing 730MPa grade ultra-high strength steel plates for high-rise buildings includes the following steps:

[0033] (1) The raw materials are smelted in a converter, refined outside the furnace and cast into a continuous casting billet to obtain a billet with a thickness of 220mm.

[0034] (2) The slab is placed in a heating furnace and heated at 1200℃ for a total time of 220 minutes.

[0035] (3) Two-stage rolling process is adopted: the rough rolling start temperature is 1085℃, the billet thickness is 70mm, the finish rolling start temperature is 930℃, the final rolling temperature is 880℃, and the steel plate with a thickness of 20mm is rolled.

[0036] (4) After rolling, the rolls are cooled by laminar flow cooling. The water temperature is 840℃, the final cooling temperature is 492℃, and then the rolls are cooled to room temperature by air.

[0037] Another preparation method includes the following steps:

[0038] (1) The raw materials are smelted in a converter, refined outside the furnace and cast into a continuous casting billet to obtain a billet with a thickness of 220mm.

[0039] (2) The slab is placed in a heating furnace and heated at 1200℃ for a total time of 228 minutes.

[0040] (3) Two-stage rolling process is adopted: the rough rolling start temperature is 1091℃, the thickness of the billet to be warmed is 150mm, the finish rolling start temperature is 930℃, the final rolling temperature is 890℃, and the steel plate with a thickness of 40mm is rolled.

[0041] (4) After rolling, the rolls are cooled by laminar flow cooling. The water temperature is 850℃, the final cooling temperature is 440℃, and then the rolls are cooled to room temperature by air.

[0042] Example 3:

[0043] The present invention discloses a method for manufacturing a 730MPa grade ultra-high strength steel plate for high-rise buildings. The chemical composition, by mass percentage of each element, is as follows: C: 0.13%, Si: 0.30%, Mn: 1.85%, P: 0.010%, S: 0.004%, Cr: 0.85%, Ni: 0.50%, Cu: 0.29%, Nb: 0.070%, V: 0.06%, Ti: 0.020%, Al: 0.048%. The balance is Fe and unavoidable impurity elements.

[0044] Furthermore, a method for preparing 730MPa grade ultra-high strength steel plates for high-rise buildings includes the following steps:

[0045] (1) The raw materials are smelted in a converter, refined outside the furnace and cast into a continuous casting billet to obtain a billet with a thickness of 220mm.

[0046] (2) The slab is placed in a heating furnace and heated at 1220℃ for a total time of 280 minutes.

[0047] (3) Two-stage rolling process is adopted: the rough rolling start temperature is 1100℃, the thickness of the billet is 65mm, the finish rolling start temperature is 920℃, the final rolling temperature is 876℃, and the steel plate with a thickness of 20mm is rolled.

[0048] (4) After rolling, the rolls are cooled by laminar flow cooling. The water temperature is 834℃, the final cooling temperature is 487℃, and then the rolls are cooled to room temperature by air.

[0049] Another preparation method includes the following steps:

[0050] (1) The raw materials are smelted in a converter, refined outside the furnace and cast into a continuous casting billet to obtain a billet with a thickness of 220mm.

[0051] (2) The slab is placed in a heating furnace and heated at 1218℃ for a total time of 286 minutes.

[0052] (3) Two-stage rolling process is adopted: the rough rolling start temperature is 1090℃, the thickness of the billet to be warmed is 124mm, the finish rolling start temperature is 900℃, the final rolling temperature is 862℃, and the steel plate with a thickness of 40mm is rolled.

[0053] (4) After rolling, the rolls are cooled by laminar flow cooling. The water temperature is 825℃, the final cooling temperature is 471℃, and then the rolls are cooled to room temperature by air.

[0054] Table 1. Chemical composition (wt.%) of 730MPa grade ultra-high strength structural steel

[0055]

[0056] Table 2 Mechanical properties of 730MPa grade ultra-high strength structural steel

[0057]

[0058]

[0059] As shown in Table 2, the mechanical properties of Examples 1-3 are as follows: yield strength ≥624MPa, tensile strength ≥750MPa, elongation ≥19%, yield strength ratio ≤0.85, low temperature impact value at -40℃ ≥166J, and Z-direction reduction of area ≥65%, all of which are higher than the requirements specified in standard GB / T19879-2015. They have good performance stability and can meet the structural design requirements of high-rise buildings in my country.

[0060] This invention employs a low-carbon, low-carbon, micro-alloying design, with the addition of small amounts of Cr, Ni, and Cu elements. Micro-alloying elements such as Nb and V precipitate during the two-stage rolling process, pinning austenite grains and inhibiting their growth, thus refining grain size and providing precipitation strengthening to ensure the high strength requirements of the steel plate. The addition of Cr, a high-solution strengthening element, significantly improves the solid solution strengthening effect of the steel plate. The appropriate addition of Ni ensures the strength of the steel plate while significantly improving its low-temperature toughness. Simultaneously, the addition of Cu provides further solid solution and precipitation strengthening, ultimately resulting in a high-performance steel plate.

[0061] The 730MPa grade ultra-high strength high-rise building steel plate provided by this invention adopts a controlled rolling and controlled cooling production process. The rolling process strictly controls the temperature and compression ratio of the two-stage rolling process, supplemented by the subsequent rapid water immersion controlled cooling method. By precisely controlling the red-hot temperature, a certain proportion of bainite and ferrite structure is obtained, while obtaining stable and excellent mechanical properties. The production process is short and the preparation method is simple.

[0062] The 730MPa grade ultra-high strength steel plate for high-rise buildings provided by this invention has excellent comprehensive properties such as low yield strength ratio, high strength, high elongation, and high and low temperature toughness, which is of great significance to the development of high-rise, super high-rise, and large-scale steel structure buildings in my country.

[0063] This invention develops high-performance 730MPa grade steel plates for construction through relatively economical composition design and controlled rolling and cooling production processes, which can meet the needs of high-rise, super high-rise, and large-scale building design in my country.

Claims

1. A 730 MPa grade ultra-high strength steel sheet for high-rise buildings, characterized by, The chemical composition in percentage by weight is: C: 0.11~0.13%, Si: 0.17~0.30%, Mn: 1.61~1.85%, P: ≤0.015%, S: ≤0.005%, Cr: 0.55~0.85%, Ni: 0.30~0.50%, Cu: 0.15~0.30%, Nb: 0.040~0.070%, V: 0.03~0.06%, Ti: 0.010~0.020%, Al: 0.020~0.050%, and the balance of Fe and inevitable impurities; The preparation steps are as follows: (1): The heating system of the slab heating furnace: the heating temperature is 1180~1220℃, and the total furnace time is 10~14min / cm; (2): The rolling process: two-stage controlled rolling, i.e. austenite recrystallization zone and austenite non-recrystallization zone rolling, and the total compression ratio is not less than 3 times: The rough rolling open rolling temperature is ≥1080℃, and large reduction is adopted in this stage; The start temperature of the finish rolling is 900~930℃, and the warm slab thickness is not less than 3.0 times of the finished product thickness, and the final rolling temperature is 860~890℃; (3): The cooling process: after rolling, it is quickly put into water, and after laminar flow cooling, the water inlet temperature is 820~850℃, the final cooling red temperature is 440℃~500℃, and then air cooling is carried out to room temperature; The final microstructure type of the prepared steel plate is bainite + ferrite microstructure, wherein the bainite amount is 85%~90%, and the ferrite amount is 10~15%.

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